Understanding Rifle Calibers (Simple Guide)
Let’s face it, getting to know rifle calibers can be a bit tough for beginners. The sheer variety of sizes, names, and uses can be confusing. But don’t worry, we’ve got you covered.
In this guide, we’ll break down rifle calibers in plain and simple terms, so whether you’re new to firearms or just looking to brush up on your knowledge, you’ll be able to understand rifle calibers easily.
What is a Caliber?
In simple terms, a caliber is the size or diameter of the bullet that a firearm uses. Imagine it as the “shoe size” for bullets. Rifle calibers are measured in millimeters or inches and play a crucial role in determining the power and purpose of a gun.
A smaller caliber means a smaller bullet, while a larger caliber means a larger bullet. Different rifle calibers are used for various types of shooting and hunting, so choosing the right one is essential for accuracy and effectiveness.
What is a Cartridge?
A cartridge, often referred to as “ammo” or “round,” is a complete package of ammunition that a firearm uses. It consists of several components:
Case
The case is usually made of brass or another metal and holds all the other parts together. It often represents the majority of a cartridge.
Primer
Located at the base of the case, the primer is a small, sensitive explosive that, when struck by the gun’s firing pin, ignites and creates a spark to start the ignition process.
Powder
The case contains a specific amount of gunpowder, which burns rapidly when ignited, producing a high-pressure gas that propels the bullet out of the barrel.
Bullet
The bullet is the actual projectile that is fired from the gun’s barrel. It’s usually made of lead or a lead-core with a copper jacket.
When you load a cartridge into a firearm and pull the trigger, the primer ignites the gunpowder, creating a high-pressure gas that propels the bullet out of the barrel toward the target.
What do the numbers mean?
The numbers in ammunition names like “Remington .222” refer to the caliber of the cartridge. Specifically, the “.222” in this case indicates the diameter of the bullet in inches. So, in the .222 Remington cartridge, the bullet’s diameter is .222 inches.
In metric units, this is roughly equivalent to 5.56mm. So, the .222 Remington cartridge fires a bullet with a diameter of approximately 5.56mm.
For Example:
Both the .222 Remington and the 5.56x45mm NATO have the same bullet diameter, roughly 5.56mm. They can fire the same .223 caliber bullet. Bullet designs are mostly interchangeable between them.
However, there’s a key difference between them in terms of chamber pressure.
The 5.56x45mm NATO is loaded to higher chamber pressures compared to the .222 Remington. This means that when you fire a 5.56x45mm NATO cartridge in a firearm chambered for .222 Remington, you are subjecting the gun to higher pressure, which can be potentially unsafe.
So, in summary, while the bullets are the same caliber, the cartridges differ in chamber pressure, and it’s crucial to use the appropriate ammunition for your firearm to ensure safety and performance.
List of Rifle Calibers & Cartridges
| Cartridge | Caliber | Suitable Game |
|---|---|---|
| .17 HMR | 4.5 mm | Varmints |
| .17 WSM | 4.5 mm | Varmints |
| .17 Hornet | 4.37 mm | Varmints |
| .22lr | 5.56 mm | Small Game |
| .22 WMR | 5.56 mm | Small Game |
| .22 Hornet | 5.56 mm | Varmints |
| .220 Swift | 5.56 mm | Varmints |
| .22-250 | 5.56 mm | Varmints, Small Game |
| .222 Remington | 5.56 mm | Varmints, Small Game |
| .224 Valkyrie | 5.56 mm | Varmints |
| .223 / 5.56 | 5.56 mm | Varmints, Small Game |
| .22 Nosler | 5.56 mm | Varmints, Small Game |
| .204 Ruger | 5.2 mm | Varmints, Small Game |
| .243 Winchester | 6.17 mm | Deer, Varmints |
| .25-06 Remington | 6.35 mm | Medium Game, Antelope |
| 6mm BR | 6 mm | Varmints, Small Game |
| 6mm Creedmoor | 6 mm | Varmints, Medium Game |
| 6.5 x 55 Swedish Mauser | 6.5 mm | Medium Game |
| 6.5 Grendel | 6.5 mm | Varmints, Medium Game |
| .260 Remington | 6.71 mm | Deer, Antelope |
| .26 Nosler | 6.71 mm | Large Game |
| 6.5-284 Norma Match | 6.71 mm | Long-Range Shooting |
| 6.5 PRC | 6.5 mm | Medium Game |
| 6.5 Weatherby RPM | 6.5 mm | Medium Game |
| 6.5-300 Weatherby Magnum | 6.5 mm | Large Game |
| .270 Winchester | 6.88 mm | Deer, Elk |
| .270 Weatherby | 6.88 mm | Deer, Elk |
| .270 WSM | 6.8 mm | Deer, Elk |
| 6.8 Remington SPC | 6.8 mm | Medium Game |
| 6.5-300 Weatherby Magnum | 6.5 mm | Large Game |
| 6.5 Weatherby RPM | 6.5 mm | Medium Game |
| 6.5 PRC | 6.5 mm | Medium Game |
| .264 Winchester Magnum | 6.71 mm | Medium to Large Game |
| .280 Remington | 7 mm | Medium to Large Game |
| 7 SAUM | 7 mm | Medium to Large Game |
| 7.62 x 39mm | 7.62 mm | Medium Game, Short-Range |
| .30-30 Winchester | 7.62 mm | Medium Game |
| .300 Blackout | 7.62 mm | Short-Range, Medium Game |
| .300 Ruger (RCM) | 7.62 mm | Medium to Large Game |
| .308 Winchester | 7.62 mm | Medium to Large Game |
| .30-06 Springfield | 7.62 mm | Medium to Large Game |
| .300 WSM | 7.62 mm | Medium to Large Game |
| .300 Winchester Magnum | 7.62 mm | Medium to Large Game |
| .30 Nosler | 7.62 mm | Medium to Large Game |
| .300 RUM | 7.62 mm | Large Game |
| .338 Lapua Magnum | 8.58 mm | Large Game, Extreme Long Range |
| .338 Federal | 8.6 mm | Medium to Large Game |
| .338 Win Mag | 8.6 mm | Large Game |
| .340 Weatherby | 8.63 mm | Large Game |
| .338 RUM | 8.59 mm | Large Game |
| .338-378 Weatherby | 8.59 mm | Large Game, Extreme Long Range |
| .350 Legend | 8.9 mm | Medium Game |
| .35 Whelen | 8.89 mm | Medium to Large Game |
| 9.3 x 62mm Mauser | 9.3 mm | Large Game |
| .375 H&H Magnum | 9.53 mm | Large Game |
| .375 Ruger | 9.5 mm | Large Game |
| .378 Weatherby | 9.65 mm | Large Game |
| .416 Ruger | 10.57 mm | Large Game |
| .416 Remington Magnum | 10.57 mm | Large Game |
| .416 Rigby | 10.57 mm | Large Game |
| .444 Marlin | 10.67 mm | Large Game |
| .450 Bushmaster | 11.43 mm | Medium Game |
| .458 Win Mag | 11.63 mm | Large Game |
| .45-70 Govt | 11.63 mm | Large Game |
| .50 BMG | 12.7 mm | Extreme Long Range |
List of Rifle Calibers to MM
Here are some of the most common rifle calibers and their bullet diameters in inches and milimeters. In my experience, here is where people are having problems understanding rifle calibers.
With time and practice, it will get easier. Make sure to look at the following table once every while, and in no time, it will get burned into your brain. Trust me, I’ve been doing this long enough…
| Caliber Name | Bullet Diameter (inches) | Bullet Diameter (mm) |
|---|---|---|
| .22LR | 0.22″ | 5.56 mm |
| .223 Remington | 0.223″ | 5.66 mm |
| 5.56x45mm NATO | 0.224″ | 5.69 mm |
| 6mm Creedmoor | 0.243″ | 6.17 mm |
| .243 Winchester | 0.243″ | 6.17 mm |
| 6.5mm Creedmoor | 0.264″ | 6.70 mm |
| 6.5mm Grendel | 0.264″ | 6.70 mm |
| .270 Winchester | 0.277″ | 7.04 mm |
| 7mm-08 Remington | 0.284″ | 7.21 mm |
| 7mm Remington Magnum | 0.284″ | 7.21 mm |
| .308 Winchester | 0.308″ | 7.82 mm |
| 7.62x39mm | 0.311″ | 7.90 mm |
| .30-06 Springfield | 0.308″ | 7.82 mm |
| .300 Winchester Magnum | 0.308″ | 7.82 mm |
| .338 Lapua Magnum | 0.338″ | 8.59 mm |
| .45 ACP | 0.451″ | 11.48 mm |
FAQ
What factors should I consider when choosing a caliber for a firearm?
Consider your intended use (e.g., target shooting, hunting, self-defense), your experience level, and factors like recoil, ammunition availability, and local regulations when selecting a caliber.
Can I use any ammunition of the same caliber in my firearm?
While ammunition of the same caliber should generally be compatible, it’s essential to use ammunition that is appropriate for your specific firearm. Refer to your firearm’s manual for guidance.
What is the difference between bullet caliber and cartridge caliber?
Bullet caliber refers to the diameter of the bullet itself, while cartridge caliber includes the entire ammunition cartridge, including the casing, primer, powder, and bullet.
How can I determine the caliber of my firearm?
The caliber of your firearm is typically marked on the barrel, slide, or frame. Consult your firearm’s markings or manual for the caliber information.
What caliber is an AR-15?
The AR-15 platform is available in various rifle calibers, and the specific caliber can vary depending on the manufacturer and configuration of the firearm. The most common caliber for AR-15 rifles is .223 Remington or 5.56x45mm NATO. These rifle calibers are often used for standard AR-15 rifles.
